The nuclear matrix-intermediate filament (NM-IF) scaffold has been prepared using a gentle, relatively non-disruptive procedure. The cell type specific proteins of the nucleus appear largely components of the NM-IF and change markedly with tissue of origin and after with transformation by carcinogens and oncogene transfection. We are developing a library of monoclonal antibodies raised to the NM-IF from a variety of carcinoma lines and onc gene transformed cells which will be used in resinless section immunoelectron microscopy. We are examining the DNA bound specifically to the NM-IF for actively transcribed and special sequences. The prompt heat shock proteins, rpoduced by translational activation of pre-existing mRNA, are entirely bound to the NM-IF. A large subset is induced by noxious agents (e.g. arsenite) and become major NM-IF constituents and monoclonal antibodies are being raised for immunoelectron microscopy and biochemical purification. Nuclear RNA synthesis and processing will be examined in stressed cells in the presence and absence of the prompt proteins to determine a possible protective role. A subfraction of hnRNA, with the properties of mRNA precursor, is released from the NM-IF by gentle salt treatment. The remaining tightly bound hnRNP appears to play an important structural role in the NM-IF. The message-like released (m-) hnRNP will be compared to the tightly bound, presumably structural (st-) hnRNP for protein composition and content of message and repetitive sequences.